Conventionally, an image has been formed on a sheet of paper using a color erasable material such as a color erasable toner in which color is to be erased by heat. There has been proposed a color erasing device which erases an image by applying heat to a sheet of paper on which the image has been formed with a color erasable material so as to erase color of the color erasable material on the sheet of paper. The color erasing process performed by the color erasing device makes it possible to form an image again on the sheet of paper, thereby allowing the reuse of the sheet of paper.
A color erasing section for heating and erasing color of a color erasable material is formed by a heat source such as a heater, a temperature sensor for detecting a temperature of the heat source, and the like. Based on the temperature of the heat source detected by the temperature sensor, the temperature of the heat source is controlled and the color erasing process is performed.
However, there is a case where the temperature sensor fails to follow the actual temperature change in the heat source and appropriate control for the heat source therefore cannot be performed. For example, due to such insufficient following, the temperature of the heat source may be increased too high and a resin component in the color erasable toner may be thus melted and attached to the color erasing section.